1. Field of the Invention
The present invention is related to an ion implanting system, and more particularly to an ion implanting system which improves utilization rate of ion.
2. Description of the Prior Art
In a fabrication process for integrated circuits, an ion implanting system is for implanting an impurity into a semiconductor material. A prior art ion implanting process includes ionizing a required impurity element, selecting the ions with a desired mass/charge ratio, targeting the selected ions toward a substrate, such as a semiconductor wafer, and implanting the impurity element into the substrate.
Referring to FIG. 1, a prior art ion implanting system is configured with a holder device 11 to hold a plurality of circularly arranged substrates 100. During an ion implanting process, the holder device 11 either rotates in a clock wise direction or counter clock wise direction, and an ion beam moves along the radial direction of the holder device 11 to scan across the whole semiconductor substrate 100. Since the rotational speed of the holder device 11 is faster and, as the device scale continue to shrink, particles in the chamber may easily cause device wafer polyline broken upon impact due to the relative motion between particle and spinning holder device 11.
Another prior art ion implanting system handles a single substrate at a time. By moving the substrate or deflecting the ion beam, the ion beam can scan across the whole substrate. As shown in FIG. 2, in order to ensure the ion beam scanning across the whole substrate 100, the ion beam must pass across the whole substrate 100. The distance D1 illustrated in FIG. 2 leaves a buffer zone for ion beam to scan off wafer, decelerating, accelerating and measuring the beam current when the scanning direction is changed. In such way, the scanning zone 200 of the ion beam, depending on beam size, could be significantly larger than the area of the substrate 100, and thus the utilization rate of the ion beam cannot be effectively increased.
Therefore, it is highly desirable to effectively increase the utilization rate of the ion beam.